First off, make sure you follow the setup requirements for DOTA 2 here:
If after following the setup requirements, PlayVIG still isn't detecting your DOTA 2 game try the following:
- Run BOTH DOTA 2 AND PlayVIG as an Administrator.
- DO NOT RUN PLAYVIG FIRST. Instead, Run the DOTA 2 client first, THEN run the PlayVIG Client. Afterwards, start your match.